This invention relates to shuttle cleaning of heat exchanger tubes and is an improvement over the concepts disclosed in the above-identified patents.
It is known from the above-identified patents to connect individual elongated cleaning element capturing cages or baskets to both ends of longitudinally extending tubes disposed in a heat exchanger housing. The tube ends are held in position at both ends by transverse tube sheets. The baskets are adapted to contain shuttlable cleaning elements, such as brushes. Fluid flowing in one direction through the tubes keeps the cleaning elements captured within their respective basket chambers, while the fluid discharges outwardly through slot-like openings in the basket walls. Upon reversal of fluid flow, the cleaning elements are forced out of their baskets and through the tubes to the baskets at the opposite tube ends to thereby perform a tube cleaning action.
Several ways have been suggested to mount the baskets in fluid flow communication with the tubes, which enter openings in the tube sheets. The inner basket ends have been press fit into the openings or into the tube ends themselves.
In other arrangements, the inner basket ends are provided with a collar which hangs from a flared lip on the tube end which is disposed beyond the outer tube sheet face.
In yet a further arrangement, such as in an embodiment disclosed in the above-identified U.S. Pat. No. 4,398,592, a retaining plate is disposed outwardly of and generally parallel to the tube sheet and cooperates with the tube sheet and the tube ends to hold the baskets in place.
It has been observed that with the latter construction there may not be proper sealing action between the various elements so that undesirable fluid leakage occurs within the system. This problem has been found to be caused by misalignment of the tube sheet relative to the heat exchanger shell, such as may be due to the heat of welding the tube sheet to the shell. As a result, the baskets and retaining plate were not properly positioned, resulting in the said undesirable fluid leakage.
It is a task of the present invention to correct for misalignment of a heat exchanger tube sheet so that there is a proper seal between the cooperative elements, including the tube sheet, tubes, baskets and retaining plate. It is a further task to correct for the misalignment in a simple low-cost but yet effective manner.
In accordance with the various aspects of the invention, longitudinally compressible means are disposed between the retaining plate and/or basket and their associated elements. In one embodiment, the compressible means is disposed between the retaining plate and the baskets so that the latter will self-adjust relative to the tube sheet and adjacent heat exchanger tubes. In another embodiment, the compressible means is disposed between the retaining plate and its peripheral mount adjacent the housing head so that the retaining plate also will self-adjust. In a further embodiment, the compressible means is disposed between the retaining plate and the tube sheet to provide an additional self-adjustment for the plate. Various combinations of the said embodiments are possible. Furthermore, various types of compressible means may be utilized.